Method of severing and milling a well casing



Sept. 28, 'O METHOD OF SEVERING AND MILLING A WELL CASING Original FiledApril 22, 1950 2 Sheets-Sheet 1 l; L i i E IN VEN TOR.

Earl J Hobiahau/ ATTORNEY Sept. 28, 1954 J. ROBISHAW 2,690,218

METHOD OF SEVERING AND MILLING A WELL CASING Original Filed April 22,1950 2 Sheets-Sheet 2 AITORNEY Patented Sept. 28, 1954 METHOD OFSEVERING AND. MILLING A WELL CASING Earl J. Robishaw, Houston, Tex.

Original application April 22, 1950, Serial No. 157,533. Divided andthis application October 6-,, 1952,, Serial- No, 313,238

2 Claims. 1

This invention relates to a. well casing milling device, and moreparticularly to an improved milling tool adapted for use in cutting andremoving pipe from the bore of. a well. This application is a divisionof the copending application of Earl J. Robishaw, Serial No.157,533,1i1ed April 22, 1950. I

In the production and operation of wells, and particularly oil wells, itis frequently necessarytoremove a portion of the casing in the well atsome predetermined location for side tracking operations, or to exposea. portion of the casing in the well at some predetermined location forside tracking operations, or to expose a producing stratum, or for otherpurposes. Thus, it may be desirable to remove a section of the casing toallow a whipstock to be set in an open: window, or the casing may be cutaway to expose a sand stratum or other potentially productive formationwhich has been previously cased off.

Such operations must frequently be conducted at great depths in the wellwhich presents serious problems in the character of the tools employedas well as in the manner in which the operation is carried out, becauseof the great weight of the operating string by which such tools areoperated and frequent deviation of the bore. of the well from thevertical.

Some of the serious problems above mentioned are caused by the inabilityof the milling tool to quickly and efiiciently mill away the casing toprovide the window therein for the purpose above mentioned. The toolsnow in use, perform. such milling operation by rotation of the cutterspro vided on the tool by rotation of the string to which the tool isattached. This straight rotat-ion causes the cutters to groove and thisgrooving stops the milling or cutting of the casing, and damages thecutters. Therefore, it is very important to prevent such grooving and,in lieu thereof, to cause the-m to wear straight across the casing beingmilled.

It is an object of the present invention, therefore, to provide amilling tool for severing and milling a well casing, which tool hascutters that are adapted to be extended across the severed end of thecasing and also to embody means for engagement with the casing to causesuch cutters to move laterally back and forth across the end of thecasing as the tool is rotated thereon. By the employment of such meansthe life of the cutters is greatly increased and more casing can be outor milled in a shorter period of time and, in addition thereto, suchmeans makes possible the cutting of pipe that, otherwise could'not becut by tools now in use. Thus, this invention now makes. it possible tohave windows milled in well casings where otherwise. it would. have beenuneconomical to have attempted to do so.

A more specific object of this invention is to provide removableeccentric means rotatably mounted or attached to a milling tool tomaintain the tool off center or eccentric of the well bore so that uponrotation of the tool it will rotate close to one side of the wall casingto be severed and away from the opposite wall whereby a simultaneous.lateral and rotation action will be imparted to the knives or blades onthe milling tool.

The above. and other objects and advantages. of the invention willappear from the following detailed description of a preferred embodimentof the same, when, considered in conjunction with the. drawings annexed,Wherein Figure 1 is av vertical, central, cross-sectional view of theinvention with the knives in retracted position;

Figure 2 is a side elevational view of the invention operativelypositioned in a well casing;

Figure 3 is a. vertical, central, cross-sectional view of the inventionoperatively positioned in the casing with the knives in extended cuttingposition;

Figure 4 is a cross-sectional view taken. along the line 4-4 of Figure3, looking in the direction indicated by the arrows; and

Figure 5 is a cross-sectional view taken along the line 55, of Figure 3,looking in the direction indicated by the arrows.

Referring to the drawings in greater detail, the numeral 1 indicates atubular cutter body or mill body having an internally threaded upper endfor attachment to the lower end of an operating string indicated at 2.The body I has an internal bore 3 forming an internal shoulder 4 nearits lower end, and a tubular stem 5, having an enlarged portion 6forming an external shoulder I, fits in the body and is supportedtherein onthe shoulder 4, with the lower end of the stem extendendportion of body I and about the lower end of the stem 5, is provided tocausethe blades, hereinaiter described, to move laterally at the sametimes they are being rotated and, thus, to produce a simultaneouscutting and sawing action which materially increases the milling speedof the tool, and also enables it to cut pipe that otherwise could not,due to its hardness, be severed by the standard milling tool now in use.

The tubular body l2, as stated above, is held in place on the lower endof the milling tool by the conical guide nut Ill. The internal facingshoulders of the lower end of the body I and the upper end of theconical nut are provided, respectively, with the anti-friction bearingsl4 and l5. Packing or seal rings l6 and H are provided between the bodyand the guide body I2 and between the guide nut l and said guide body,respectively, to prevent entrance of foreign matter into the bearings l4and I5.

The outwardly extending, spaced, members, or ribs I9 are provided on theperiphery of the body l2 for engagement with the inside of the wellcasing as that shown at 20. These ribs or radially extending members maybe formed integrally with the body or shaped in any preferred manner toaccomplish the desired purpose. As shown in Figure 5, these ribs l9 areprogressively widened, or extended outwardly, radially of the body l2,thereby providing an outside diameter for the assembly that is offcenter or eccentric with the axial bore of the body l2 through which thestem is extended.

The cutter body I has an outwardly thickened portion 22 locatedapproximately centrally of the body, and a reduced lower end portion,the portion 22 being provided with side slots 23, whose upper marginsextend out at substantially right angles to the axis of the body formingshoulders 24. Pivotally mounted in the slots 23 are the cutter blades26, pivoted on pivot pins 21, each of which has a head 29 at one end anda hole 30 at the other end for the reception of a cotter pin or othersecuring means.

The slots 23 are sufficiently long to permit the blades 26 to beretracted into them in inactive position, as seen in Figure l. Theblades are extended inwardly beyond their pivots and the inner ends arereduced in width in order to pro vide clearance sufficient to permit theouter cutting portions of the blades to be retracted into the slots whenin inactive position, as shown in Figure 1.

A bushing 32 is disposed in the body in engagement with a shoulder 33therein, and a cylinder 34 is carried on the upper end of the bush ingby an enlarged portion 35, so that the cylinder is spaced somewhat fromthe bushing to provide an annular passage 36. Openings 3'! are providedin the cylinder communicating with the passage 36 and the interior ofthe cylinder. The cylinder is spaced at its lower end from the inside ofthe body to form a continuation of the passage, as will be seen inFigures 1 and 3. Packing material 38 may also be provided on the cylinder 34 so that the cylinder is retained securely in place when thebody is attached to the string 2. The cylinder 34 is also provided witha beveled seat 40 at its lower end.

Mounted in the cylinder 34 is a piston 4|, carrying a piston ring 42held on the upper end of the piston by a washer 43 and nut 44 secured tothe threaded extension 45. The piston has a passage 46 opening into theinterior of the cylinder above the piston, and leading into sidepassages 48, which open laterally into the cylinder below the pistonring 42, as seen in Figures 1 and 3.

The piston has a tapering shoulder 50 which 4 fits against the beveledseat 40 when the piston is in its upper position.

An annular recess 52 is provided in the piston for the reception of theinward ends of the cutter blades 26 to operate the knives when thepiston moves up or down, and the lower end of the piston forms a seatfor a spring 54 which bears on an internal shoulder 55 in the stem 5 tourge the piston upwardly in the cylinder.

Vertical grooves 56 are formed about the periphery of the enlargedportion 6 of the stem 5, as seen in Figure 4, to permit the passage offluid between the body and the stem and these grooves communicate withthe interior of the tubular stem by passages 51 as indicated in dottedlines in Figure 1.

From an examination of the drawings it will be seen that in thecondition of the device shown in Figure 1, fluid from the string maypass through the passages 46 and 48, into passage 36 and downwardlythrough grooves 56 and passages 51 into the passage 6|] of the stem andthence into the casing below the tool. In this condition of the tool thepiston 4| is in its upper position, and the bottom of the cylinder isclosed by the tapered shoulder 50 so that flow of fluid is restrictedand the piston may be forced downwardly by an increase of pressure inthe string.

When the piston is moved downwardly, by the pressure of fluid in thestring, overcoming the force of the spring 54 to occupy the positionseen in Figure 3, fluid from the string may flow through holes 31 andtake the course previously described, and fluid also flows throughpassages 46, 48 and out of the bottom of the cylinder 34, so that theflow will be greater in the condition of the device shown in Figure 3,than in that shown in Figure 1.

In using the milling device, the same is attached to an operating stringand lowered into the well, in the condition seen in Figure 1, whereinthe knives 26 are retracted and the piston 4| is in its upper position.When the tool has reached the desired location opposite the portion ofthe casing 20 to be milled, the fluid pressure in the string can besuitably increased, moving piston 4| downwardly and forcing the knivesinto cutting engagement with the casing. Rotation of the string thenresults in cutting through the casing at the selected location. Afterthe casing has been severed, the knives 26 will be extended through theopening formed and brought into cutting relation with the severed end ofthe casing. The knives then bear against the shoulders 24 at the upperextremities of the slots 23, and the pressure exerted by the blades inmilling the casing may be regulated by controlling the weight appliedthereon through the operating string. Subsequent rotation of the stringwill then cause the knives to mill away the casing to the extentdesired.

It is to be noted that the engagement of the spaced members or ribs l9with the casing below the blades 26 maintains the vertical axis of thetool off center with relation to the vertical axis of the casing or boreof the well. Upon rotation of the string the body |2 of the eccentricguide assembly remains substantially stationary by the extended ribs l9contacting one side of the wall of the casing. However, the body ispermitted to rotate relative to the body 22 by the bearings 4 beinglocated between such bodies. Thus, the body of the tool rotates close toone side of the wall casing and away from the opposite wall to producethe simultaneous cutting action of the blades as hereinabove explained.

As previously explained, when the device is in the condition shown inFigure 1, and during the operation of severing the casing, fluid maypass down through the tool and on down into the casing, whence it flowsupwardly about the eccentric guide 12 and passes up out of the wellcarrying with it any cuttings or other material.

In the condition of the device seen in Figure 3, however, with theknives fully extended, and the piston in its down position, a fullcirculation of fluid through the tool takes place, thus providing forthe disposal of the relatively greater quantity of cuttings formedduring the milling operation.

Upon completion of the milling the tool can be removed from the well bywithdrawing the operating string, and the blades will be retracted forthis purpose by operation of the spring 54 urging the piston 4| upwardlyto the position illustrated in Figure 1. Should the blades fail toretract they will be pressed inwardly to retracted positionby engagementwith the casing above the milled-out portion as the tool moves upwardlyout of the well.

By suitably regulating the pressure exerted on the cutters, bycontrolling the weight applied by the operating string, the speed of themilling operation can be adjusted to satisfy particular operatingconditions, such as the hardness of the material of the casing.

I claim:

1. The method of operating a milling tool to mill away a section ofsevered casing in a cased bore hole wherein the tool comprises a bodyattachable to an operating string for rotation thereby and at least onecutter blade mounted on the body for movement from a positionsubstantially confined within the peripheral outline of the body to asubstantially radial position wherein the blade is engageable with asevered end edge of the casing, the steps comprising: rotating the toolwithin the casing with the cutter blade in its radial position and insweeping engagement with the entire circumference of the severed casingend edge; and maintaining the axis of rotation of the tool substantiallyfixed and eccentric with respect to the axis of the casing.

2. The method of operating a milling tool to mill away a section ofsevered casing in a cased bore hole wherein the tool comprises a bodyattachable to an operating string for rotation thereby and a pluralityof equi-length cutter blades mounted on the body for movement frompositions substantially confined within the peripheral outline of thebody to substantially radial positions wherein the blades are engageablewith a severed end edge of the casing, the steps comprising: rotatingthe tool within the casing with the cutter blades in their radialpositions; maintaining the axis of rotation of the tool substantiallyfixed and eccentric with respect to the casing axis; and advancing thetool relative to the casing with each cutter blade in sweepingengagement with the entire circumference of the severed casing end edge.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,334,224 Campbell Mar. 16, 1920 2,299,528 Conner Oct. 20,1942 2,412,859 Barnes Dec. 1'7, 1946

